Treatment for leather



United States Patent 3,494,977 TREATMENT FOR LEATHER Roger J. Heit,Midland, Mich, gssignor t0 Dow Corning Corporation, Midland, Mich, acorporation of Michigan No Drawing. Filed Mar. 28, 1968, Ser. No.716,994 Int. Cl. C08g 47/10, 31/24 US. Cl. 260825 8 Claims ABSTRACT OFTHE DISCLOSURE ltlle NHECHZCHZNHCHZOHCHzSiOg/g and 16 g. of

c llleaslo SiO :4 SiD/leO SiMe in which R is an alkyl radical of 16 to24 carbon atoms.

This invention relates primarily to treatment of suede leather and othertypes of unfinished 1 leather employed in the manufacture of shoes andgarments. One of the problems with leather garments occurs when they aredry cleaned. The dry cleaning solvent extracts much of the fat liquorfrom the leather, thereby rendering it hard and undesirable by way offeel. In present operation in the dry cleaning shop the leather garmentis immersed in the dry cleaning solvent which generally containsneatsfoot oil and thereafter removed from the solvent and dried and thensprayed with an emulsion or solution of wax or some other material toenhance softness. After such treatment the water or solvent isevaporatediand it is necessary to brush the leather several times inorder to obtain the original nap and softness. In general, at least twobrushings is required and these are usually hand operations. If waterrepellency is desired, the garment is sprayed with a suitable product.Consequently, the dry cleaning of leather garments is quite expensive.

Also, dry cleaning of present leather garments often removes largequantities of dye from the leather, particularly in those cases wherethe less expensive non-acidic dyes are employed. Consequently, it isoften necessary for the dry cleaner to add a dye to the leather afterdry cleaning. All of this adds additional expense to the dry cleaning ofthe garment.

It would be highly desirable to have a material which could be added tothe dry cleaning solution or which could be applied to the leatherimmediately after dry cleaning which would obviate most of the brushingstep and which would impart to the leather a high degree of waterrepellency and would maintain the original softness and high nap of thesuede leather. In addition, it would be highly desirable to have amaterial which Unfinished leather refers to leather which is notfinished with a coating of polymeric materials such as acrylates.

3,494,977 Patented Feb. 10, 1970 "ice would prevent or retard theextraction of dye from the leather during dry cleaning.

In adition to dry cleaning there are instances in which a suitablematerial could be added at the tannery in order to enhance the waterrepellency and the softness and luster of suede leather. This isparticularly true with respect to pigskin which is at present beingemployed to make shoes called Hush-Puppies.

One of the difiiculties with such shoes is that although they are quitecomfortable they tend to absorb large quantities of water and to hardenon use and to become quite dirty. Consequently, such shoes are wornprimarily in warmer or drier climates, such as California or Florida.However, they also have extensive markets in the colder and/or wetterregions of the country. If properly treated the market for such shoes inthe colder and wetter regions could be greatly enhanced because of theirresistance to deterioration by water.

This invention relates to a method of treating leather which comprisesimpregnating the leather with 1) a copolymer of units of the formula and(B) Me SiO units in amount of at least 3 moles 2 of (B) per mole of (A),and (2) a polysiloxane of the unit formula hie RSi O which can containup to 96 mol percent copolymerized Me SiO units in which siloxanes (l)and Y is an acid anion,

R is an alkylene radical of 2 to 6 inclusive carbon atoms,

R is a lower alkyl radical,

a has a value from 0 to l,

b has a value from 0 to 2, and

R" is an alkyl or an aralkyl radical of at least 9 carbon atoms, and theweight ratio of (l) to (2) is from 4:1 to 0.75:1.

This invention also relates to compositions of matter consistingessentially of mixtures of (l) and (2). The term consisting essentiallyof means that the compositions can contain other ingredients normallyemployed in the treatment of leather which do not materially change theeffects of the combination l) and (2).

(1) and (2) can be applied to the leather either as a mixture (i.e.,simultaneously) or they can be applied separately. In either case theapplication can be from solvent solutions or aqueous solutions oremulsions. The solvent solutions are generally preferred when employing(1) and (2) during dry cleaning of a leather garment. Aqueous emulsionsare generally preferred when the (1) and (2) are applied to leather atthe tannery during processing of the leather. The amount of (l) and (2)used on the leather is not critical, but can vary from 0.5 to 25% total(1) and (2) by weight based on the 2 Based on unit weight (i.e., 74 forMeaSiO).

dry weight of the leather depending upon the particular type of leatherand the desired eflect.

The term leather employed herein includes animal hide in general,including cowhide, pigskin, sheepskin, horsehide, etc. As mentionedabove, the treatment of this invention is particularly suitable to suedeleather, that is leather having a nap, and such leather, as is wellknown is primarily employed in the manufacture of coats, jackets, andspecial types of shoes.

Copolymer (1) employed in this invention is a copolymer of anaminoalkylsiloxane of the type shown and dimethylsiloxane. For thepurpose of this invention R can be any alkylene radical of from 2 to 6carbon atoms, such as CH CH CH CH CH and R can be any lower alkylradical such a methyl, ethyl, propyl, isopropyl or butyl and a can beor 1. Therefore the amine can be substituted on a silicon with no othersubstituents or on a silicon with one other substituent.

As can be seen the amine can be employed per Se or in the form of anamine salt. Thus, Y can be any acid anion either from a carboxylic acidor other organic acids such as sulfonic acid, or phosphinic acid or acidalkyl sulphonate; or it can be derived from inorganic acids such ashydrochloric, hydrobromic, sulfuric, nitric, phosphoric, etc.Preferably, Y is an anion of a monocarboxylic acid, such as acetic,formic, propionic, hexoic, etc. In general, it is preferred to employthe amine salt when the composition is to be used in the form of anaqueous dispersion. When the composition is to be employed in the formof solvent solutions, it is preferred that the amine per se be used.

As is noted, the ratio of aminosiloxane units and dimethylsiloxane unitsmust be such that there is at least 3 mols of dimethylsiloxane units permol of aminosiloxane unit. The upper limit of this ratio is notcritical, however, it is preferred that there be no more than 1000dimethylsiloxane units per amine siloxane units with optimum resultsoften being obtained with no more than 100 Me SiO units per aminesiloxane unit.

Ingredient (2) of this invention can be an alkylmethylsiloxane or anaralkylmethylsiloxane of the formula RMeSiO in which R" can be ahydrocarbon radical having at least 9 carbon atoms such as alkylradicals, such as decyl, dodecyl, tetradecyl, octadecyl, C H andmyricyl; or any aralkyl radical such as beta-phenylpropyl If desired,composition (2) can have dimethylsiloxane copolymerized with the R"MeSiOand the dimethyl can be present in amounts up to 96 mol percent of thetotal composition (2).

Both components (1) and (2) can have silicon-bonded hydroxyls on theends of the chain or they can be endblocked with triorgano-substitutedsiloxanes or with any other of the endblocking units normally employedin commercial siloxanes such as alkoxy groups, acetoxy groups, etc.

Also the structure of (l) and (2) is not critical since these materialscan be in the form of linear, branched or cyclic molecules or mixturesthereof.

In addition to (l) and (2), the leather can also be treated with othermaterials normally employed in leather to perform specific functionstherein, such as, for example, glutaraldehyde, or other materials usedin the tanning or fixing processes. The additional materials can be usedin admixture with or in Separate steps with respect to (1) and (2).

The following examples are illustrative only and should not be construedas limiting the invention which is properly delineated in the appendedclaims. Me is employed herein as an abbreviation of the methyl radical.

EXAMPLE 1 375 g. of

Mes HO S iO H having a viscosity of about 250 cs. at 25 C. was mixedwith 125 g. of

Me (MeO) SiCH JHCHZNHCHZCIENH:

and heated at about C. for 1.5 hours to copolymerize the ingredients. 34g. of the above product [designated (1)] was mixed with (2) 16 g. of

we a MeSiO SiO 24 SiMeO) -,SiMe

in which R represents radicals of the formula C H to (lliez) Bile MBgSiOSiO 4(Si0 SiMes C20H41; and 50 g. of perchloroethylene.

Three sheepskin suede leather amples having a dry weight of 700 g. werewashed with isopropanol and then covered with 5 gallons ofperchloroethylene. To the leather was added the above solution of 1) and(2) in amount such that there was a total of 6% by weight (1) and (2) inthe treating bath based on the dry weight of the leather. The leatherwas tumbled for one hour then removed from the vessel and dried for 48hours at roomtemperature and then 15 minute at 70 C. The spray rating ofthe resulting leather was 70 based on Federal Test Method 5526 (US.Government publication). It did not water spot when a drop of water wasapplied and allowed to evaporate. The gloss and feel of this leather wasexcellent and the nap was very prominent.

EXAMPLE 2 53.4 g. of (1) of Example 1 and 26.6 g. of (2) of Example 1was dissolved in 15 g. of an aliphatic hydrocarbon solvent and 5 g. ofisopropanol. The above solution was added to an aliphatic hydrocarbonsolvent in a commercial dry cleaning establishment during the drycleaning of a suede leather coat in the amount of 4% by weight of (A)and (B) based on the dry weight of the leather. The garment was tumbledfor 25 minutes, then centrifuged to remove the solvent and dried atroomtemperature for 48 hours and then 10 minutes at 65 C. After lightbrushing the coat had excellent sheen, nap and softness. It did notwater spot and had a spray rating of 65.

EXAMPLE 3 53.4 g. of (1) of Example 1 was mixed with 70 g. of xylene and26.6 g. of

Me CruHzr 0141120 Me SiO (S iO)2o(Si0 (SlO)4osiMea H CHMe Suede leatherwas covered with 5 gallons of xylene and the above composition was addedin amount of 4% by weight of (l) and (2) based upon the dry weight ofthe leather. The mixture was agitated for 30 minutes and then removedfrom the solution, dried 48 hours at Made by the addition of a mi t ofolefinh. ranging from CIQHS: t0 zoHio to cu r 5 room-temperature andthen 15 minutes at 70 C. The resulting leather was soft and hadexcellent lustre and a spray rating of 70. It did not water spot.

EXAMPLE 4 This example is given by way of comparison to show thatdimethylsiloxane cannot be substituted for (2) in the compositions ofthis invention. The process of Example 1 was repeated except thatthree-fourths of composition (2) was replaced by lYlea Me si (Si 0 SiMe3having a viscosity of 350 cs. The resulting suede leather had a poorappearance and the spray rating was less than 50.

EXAMPLE This example illustrates the step-wise addition of (l) and (2).Four samples of pigskin suede leather were washed with water for 15minutes at 130 F. then drained and covered with water in a Najortwasher. A 40% aqueous emulsion of (2) of Example 1 was added in amountto give 5% by weight (2) based on the dry weight of the leather. Theleather was then agitated for 30 minutes at 130 F. 2.5% glutaraldehydewas added based on the dry weight of the leather and agitation wascontinued 45 minutes at 130 F. 2.4 g. of a 0.2% by weight solution ofsodium bicarbonate was added to the leather in three portions atintervals of 5 minutes. This was for the purpose of adjusting the pH ofthe leather. The leather was washed 15 minutes, drained and refloated inwater at 130 F.

A composition 1) was prepared by reacting 37.5%

MeC O OH Me (MeCOOH-HaN CHzCHzNHCHzJIHCHzSi 02/2) 1 2 0) by weight of ahydroxyl-endblocked dimethylpolysiloxane fluid having 1.63% by weightsilicon-bonded hydroxyl, 12.5% by weight hide (N180)SlCHzCH2CHNHCH2CH2NH2 and 6.8% by Weight acetic acid in 43.2% by weightisopropanol. This solution was added to the leather bath in amount togive 5% by weight (1) based on the dry weight of the leather. The bathwas then agitated 30 minutes at 130 F. The leather was then removed andwashed with water at 90 F. It was dried, staked, buffed and dry milledin the usual manner employed in tanneries. The resulting leather hadgood tracking, good temper and good water resistance, as shown by thefact that it absorbed only 21.2% by weight water after 4000 flexes onleather flex tester No. 1002, sold by Dow Corning Corporation, Midland,Mich.

EXAMPLE 6 Equivalent results were obtained when the following silanesare substituted for the silane in composition (1) of Example 1. H NCH CHNH(CH Si(OMe) H NCH CH NH(CH Si (OMe 3 and EXAMPLE 7 Equivalent resultsare obtained when the following amine salts are substituted for theacetate salt (1) of Example 5.

4 The product was a copolymer of the average formula 6 That which isclaimed is: 1. A method of treating leather which comprises impregnatingthe leather with (1) a copolymer of the unit formula and (B) units ofthe formula Me SiO in amount of at least 3 mols of (B) per mole of (A),and

( 2) a polysiloxane of the unit formula Me RS iO which can contain up to96 mol percent copolymerized Me SiO units in which siloxanes 1) and (2)Y is an acid anion, R is an alkylene radical of 2 to 6 inclusive carbonatoms, R is a lower alkyl radical, a has a value from 0 to 1, b hasvalue from 0 to 2, and R" is an alkyl or an aralkyl radical of at least9 carbon atoms, the weight ratio of (1) to (2) being from 4:1 to 0.75:1.

2. The method in accordance with claim 1 in which the leather isimpregnated with an organic solvent solution of (1) and (2).

3. The method in accordance with claim 2 in which (1) is a copolymer ofI HaNCHeCHgNHCHzCHOHzSiO z and Me SiO and (2) is a copolymer of and MeSiO in which R" is an alkyl radical of at least 9 carbon atoms.

4. The method of claim 1 in which (B) is present in amount from 3 to 100mols per mol of (A).

5. The method of claim 3 in which (B) is present in amount of from 3 to100 mols per mol of (A).

6. A composition of matter consisting essentially of a mixture of 1) acopolymer of the unit formula (Y-)bH; NCH2CHzNHRSiO '2 and (B) units ofthe formula Me SiO in amount of at least 3 mols of (B) per mole of (A),and (2) a polysiloxane of the unit formula which can contain up to 96mol percent copolymerized Me SiO units in which siloxanes (1) and (2) Yis an acid anion, R is an alkylene radical of 2 to 6 inclusive carbonatoms, R is a lower alkyl radical, a has a value from 0 to 1, b has avalue from 0 to 2, and R" is an alkyl or an aralkyl radical of at least9 carbon atoms, the weight ratio of (1) to (2) being from 4:1 to 0.75:1.

7. The composition of claim 6 in which (1) is a copolymer ofNHzCHzCHzNHCHzCHCHgSiOa/z and Me SiO and ,(2) is a copolymer of 1 and MeSiO in which R" is an alkyl radical of at least 9 carbon atoms.

8. The composition of claim 6 in which (B) is present in amount of from3 to 100 mols per mol of (A).

SAMUEL H. BLECH, Primary Examiner US. Cl. X.R.

